In a communication process, power of a signal often changes over time because of factors such as channel fading, load magnitude, and power control, so that a communication receiver is required to have a certain reception range to ensure correct reception of the signal. AGC may maintain power of a received signal within a stable range, and by predicting signal power in a future time period, generate an appropriate amplification gain so that a signal at an input port of an ADC (Analog Digital Converter, analog-to-digital converter) or in a digital domain is stabilized at a basically-fixed power level or within a small dynamic range of power levels. When an AGC gain to be used in a next period is obtained, two functions need to be ensured at the same time:
1. A radio frequency device and an analog device and various nodes in the digital domain need to be non-saturated or as less saturated as possible.
2. Useful signal power is adjusted to a certain power level to reduce a dynamic range of the received signal power.
In the prior art, the AGC gain used for the next period is obtained using the following three schemes:
Scheme I: Set signal power of a target Received Signal Strength Indication (RSSI) that collects statistics about signal power of a current wideband RSSI (WB-RSSI), and then calculate the AGC gain that may be used in the next period by subtracting the signal power of the WB-RSSI from the target RSSI and adding a currently-used gain. When blocking is caused by presence of strong signal interference, this segment of signals may be discarded. The WB-RSSI refers to a RSSI obtained by collecting statistics about data that has undergone ADC conversion, and the RSSI obtained by collecting statistics includes signal power outside a useful signal bandwidth.
Scheme II: Set signal power of a target RSSI, collect statistics about signal power of a current narrowband RSSI (NB-RSSI), and then calculate the AGC gain that may be used in the next period by subtracting the signal power of the NB-RSSI from the signal power of the target RSSI and adding a currently-used gain. When blocking is caused by presence of strong signal interference, this segment of signals may be discarded. The NB-RSSI refers to a RSSI obtained by collecting statistics about data that has passed through a filter, and the RSSI obtained by collecting statistics does not include signal power outside a useful signal bandwidth.
Scheme III: First, allow a power level of a useful signal to fluctuate within a certain dynamic range, determine a target power range of the useful signal, subsequently collect statistics about signal power of a current NB-RSSI, and obtain an acceptable AGC gain range by subtracting the signal power of the NB-RSSI from the target power range of the useful signal; then, collect statistics about signal power of a current WB-RSSI and calculate a non-saturated AGC gain range according to the signal power of the WB-RSSI; finally, obtain an intersection of the acceptable AGC gain range and the non-saturated AGC gain range to determine any point in the intersection to be the AGC gain that may be used in the next period.
However, in the first scheme of the prior art, the use of the WB-RSSI can only ensure that the radio frequency device and the analog device and the various nodes in the digital domain are non-saturated; in the second scheme, the use of the NB-RSSI can only ensure that the useful signal power is adjusted to a certain power level to reduce the dynamic range of the received signal power; and in the third scheme, both the WB-RSSI and the NB-RSSI are used, and when the signal interference is very strong, it is possible to calculate that there is no intersection between the acceptable AGC gain range and the non-saturated AGC gain range so that the AGC gain that may be used in the next period cannot be determined.
Therefore, when the AGC gain used for the next period is obtained in the foregoing three schemes of the prior art, it cannot be ensured that the radio frequency device and the analog device and the various nodes in the digital domain are non-saturated and that the useful signal power is adjusted to a certain power level at the same time.